Energy giant SSE has become the latest Big Six firm to report sliding profits and falling customer registrations.

The company lost 430,000 customers last year, with domestic accounts falling from 7.23 million to 6.8 million as competition intensified and pre-tax profits fell by 6% to £1.45 billion.

Its revenue rose 8% to £31.23 billion over the period as cold weather bolstered energy usage.

The news comes ahead of the planned merger of the company’s retail business with npower, which the UK’s competition watchdog has referred for an in-depth investigation.

An SSE spokesperson said: “While electricity tariffs increased to recognise rising non-energy costs, overall profits were also impacted by customer account losses and the introduction of price caps for certain customer groups, offset by ongoing efficiency savings.

“The business also benefited, in the last quarter of the financial year, from higher customer energy consumption due to unseasonably cold weather.”